Determination of Mn2+ using a paper-based flexible electrochemical sensor modified by NiFe2O4 and CeO2 nanoparticles

Abstract

NiFe₂O₄, a spinel compound, has drawn significant interest from researchers due to its high natural saturation and remarkable electrocatalytic properties. Simultaneously, CeO₂ can introduce structural defects to enhance the functional properties of materials. Synthesizing these compounds at a nanoscale level imparts them with unique characteristics, which are often absent in their normal forms. In this study, we developed a paper-based electrochemical sensor via the modification of a laser-induced graphene (LIG) electrode with NiFe₂O₄ and CeO₂ nanoparticles. Various characterization approaches were used to determine the morphological structure and electrochemical performance of the electrode. These analyses demonstrated that NiFe₂O₄ and CeO₂ nanoparticles improved the electrocatalytic properties of the sensor. The nanoparticles modified the electrode's surface by creating additional active sites for improved detection. Density functional theory (DFT) calculation results further illustrated that the interaction between two nanoparticles helped in improving the electron transfer and adsorption abilities of the electrode. The sensor exhibited a wide linear range from 8 μg L⁻¹ to 2 mg L⁻¹, a low limit of detection (LOD) of 1.72 μg L⁻¹, and remarkable anti-interference ability and reproducibility under optimized conditions. This sensor was successfully used to accurately detect Mn²⁺ in real groundwater samples. This study offers a promising way for the rapid, portable and accurate detection of Mn²⁺ using a paper-based electrochemical sensor.